This invention relates to the technical field of display devices such as a liquid-crystal display and a CRT (cathode-ray tube), more particularly to a display device optimal for use as a monitor for medical diagnostic apparatus.
The diagnostic images taken with medical diagnostic apparatus such as MRI diagnostic apparatus, X-ray diagnostic apparatus and apparatus for CR (computed radiography) diagnostic apparatus, for example, FCR (Fuji Computed Radiography made of Fuji Photo Film Co., Ltd.) are usually recorded on light-transmitting image recording films such as X-ray films and light-sensitive materials in film form and thereafter reproduced as light-transmissive images. The films showing the reproduced diagnostic images are set on a light source device called a “Schaukasten” and illuminated with a backlight so that the images are viewed for diagnostic purposes.
Medical diagnostic apparatus usually have a monitor (display) such as CRT, either built-in or connected, for viewing the diagnostic images taken with the apparatus. Diagnosis is performed on the basis of the image output to the monitor or the diagnostic images to be output on films are checked, adjusted or otherwise processed on the monitor.
The diagnostic images displayed on the monitor are usually monochromatic (in black and white) and, in principle, diagnosis is based on the difference in image density. To achieve correct diagnosis, it is required that subtle differences in density be finely identified even if the diagnostic image reproduced on a film has high densities in excess of 2.0. To meet this requirement, the “Schaukasten” (lantern slide) emits very bright light. Monitors for medical diagnostic apparatus are also required to be capable of displaying comparably sharp images and, to this end, very bright display is performed.
However, the diagnostic images are not the only representations on the monitor for medical diagnostic apparatus and usually non-image representations such as characters for the name of the image (file name) and menus (e.g., tool bars and windows) for executing various operations by GUI (graphical user interface) are also displayed. For some operational reasons, only characters and menus may be displayed. If characters and menus are unduly bright, visibility is impaired to reduce the efficiency in operation; what is more, great stress is imposed on the viewer's eyes.
Some monitors have a device for adjusting the brightness of the display but this is in most cases manual and only adapted to perform continuous adjustment in brightness; hence, it is poor in operability.